You can create a simple PropertyModel to hold the value your form is
trying to set. Here is an example:
public Pageextends WebPage {
private List letters = Arrays.asList(new String[] {"A","B","C" }));
public String selected ="B";
public Page() {
Form form =new Form("form");
DropDownChoice choice=new DropDownChoice("ddc",new
PropertyModel(this,"selected"), letters);
}
}
The example is from:
https://cwiki.apache.org/WICKET/dropdownchoice-examples.html. It is
missing the generics if you are working in 1.4.x, but it demonstrates
the process well.
The model object here is the "selected" string. When the form saves it
will set the "selected" string with the value in the drop down.
On 3/25/2011 9:40 AM, Jim Goodwin wrote:
I'm trying to follow the example in the Javadoc for DropDownChoice
which says:
Java:
List SITES = Arrays.asList(new String[] { "The Server Side", "Java
Lobby", "Java.Net" });
// Add a dropdown choice component that uses Input's 'site'
property to designate the
// current selection, and that uses the SITES list for the
available options.
// Note that when the selection is null, Wicket will lookup a
localized string to
// represent this null with key: "id + '.null'". In this case, this
is 'site.null'
// which can be found in DropDownChoicePage.properties
form.add(new DropDownChoice("site", SITES));
HTML:
<select wicket:id="site">
<option>site 1</option>
<option>site 2</option>
</select>
I follow this quite closely. The code is inside a form:
List<String> recCapNames = new ArrayList<String>();
for (Capability cap : recognizedCaps)
recCapNames.add(cap.toString());
final DropDownChoice permissionDropDown = new
DropDownChoice(
"permissionDropdown", recCapNames);
add(permissionDropDown);
<select wicket:id="permissionDropdown">
<option>P1</option>
<option>P2</option>
</select>
The page renders fine. The dropdown shows the right elements in the
list when I pull it down,
and allows me to select one, etc. But when I hit any button on the
form it pukes,
complaining about trying to setModelObject on a null model.
(I have several buttons on the form, only one of which is related to
the DropDownChoice,
and they all fail the same way. Their onSubmit() methods never get
reached: some sort of
general process of form-handling is run first, and that's where the
exception happens.)
Stack dump below. Wicket 1.5 RC2.
Any ideas?
Thanks in advance
Jim
Stackdump:
Root cause:
java.lang.IllegalStateException: Attempt to set model object on null
model of component:
AdministerGroupForm:permissionspanel:permissionpanelform:permissionDropdown
at
org.apache.wicket.Component.setDefaultModelObject(Component.java:3006)
at
org.apache.wicket.markup.html.form.FormComponent.updateModel(FormComponent.java:1038)
at
org.apache.wicket.markup.html.form.Form$FormModelUpdateVisitor.component(Form.java:221)
at
org.apache.wicket.markup.html.form.Form$FormModelUpdateVisitor.component(Form.java:192)
at
org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:274)
at
org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:263)
at
org.apache.wicket.util.visit.Visits.visitPostOrder(Visits.java:246)
at
org.apache.wicket.markup.html.form.FormComponent.visitComponentsPostOrder(FormComponent.java:384)
at
org.apache.wicket.markup.html.form.Form.internalUpdateFormComponentModels(Form.java:1669)
at
org.apache.wicket.markup.html.form.Form.updateFormComponentModels(Form.java:1634)
at org.apache.wicket.markup.html.form.Form.process(Form.java:807)
at
org.apache.wicket.markup.html.form.StatelessForm.process(StatelessForm.java:61)
at
org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:743)
at
org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:685)
at java.lang.reflect.Method.invoke(Unknown Source)
at
org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:259)
at
org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:215)
at
org.apache.wicket.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:171)
at
org.apache.wicket.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:157)
at
org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:706)
at
org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:63)
at
org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:212)
at
org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:253)
at
org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:138)
at
org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:194)
at
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1323)
at
org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:474)
at
org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
at
org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:517)
at
org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226)
at
org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:935)
at
org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:404)
at
org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:184)
at
org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:870)
at
org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
at
org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
at org.eclipse.jetty.server.Server.handle(Server.java:346)
at
org.eclipse.jetty.server.HttpConnection.handleRequest(HttpConnection.java:596)
at
org.eclipse.jetty.server.HttpConnection$RequestHandler.content(HttpConnection.java:1068)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:807)
at
org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:220)
at
org.eclipse.jetty.server.HttpConnection.handle(HttpConnection.java:426)
at
org.eclipse.jetty.server.bio.SocketConnector$ConnectorEndPoint.run(SocketConnector.java:241)
at
org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:528)
at java.lang.Thread.run(Unknown Source)
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